Hepatitis B virus (abbreviated as “HBV” hereinafter) and hepatitis C virus (abbreviated as “HCV” hereinafter) have been discovered so far as etiologic viruses of blood-borne infectious hepatitis. Diagnostic methods for the both viruses have already been established, and they were early introduced into the screening of blood for blood transfusion in this country. As a result, it has become possible to substantially completely prevent novel infection cases in blood recipients for the both hepatitis viruses.
However, even after the diagnostic methods for HBV and HCV were established, cases suspected of cryptogenic viral hepatitis constitute 5-10% of the whole hepatitis cases. These cases have not been considered to be caused by hepatitis A virus, which is a hepatitis virus of non-blood-borne infectious type, hepatitis E virus, hepatitis F virus, which has been reported only in India and its existence itself is doubted, and hepatitis D virus, which is a defective hepatitis virus, and possible existence of unknown hepatitis virus has been suggested.
Gene sequences of viruses considered to be etiologic agents of these hepatitis cases were reported in succession by Abbott, U.S.A. in 1995, and then by Genelabs Technologies in 1996, and designated as GBV-C and HGV, respectively. However, these viruses became to be considered identical one afterwards based on comparison of their sequences (abbreviated as “GBV-C/HGV” hereinafter). Studies about involvement of GBV-C/HGV in cryptogenic viral hepatitis are being actively performed also in this country. As a result, it has thus far considered at least that GBV-C/HGV does not account for all of the causes of non-B, non-C hepatitis of unknown etiology, because expression of hepatitis symptoms has been slight in its infection cases while it may be transmitted via hematic route, and therefore an unknown virus might be responsible for the cryptogenic hepatitis.
Existence of an unknown hepatitis virus causing blood-borne infectious hepatitis has been suggested as described above, and it has been desired to discover this unknown hepatitis virus, and elucidate genetic, molecular-biological and epidemiological characteristics of the virus, thereby realizing more complete prophylactics, diagnostic methods and therapies for hepatitis.
In other words, in order to develop diagnostic methods and therapeutic methods of hepatitis caused by an unidentified virus, desired are to obtain genetic information of the virus, to determine virus-specific gene sequences and amino acid sequences, to determine locations of epitopes, to establish production methods of biological materials containing the epitopes, to establish production methods of antigens which specifically react with antiviral antibodies, to provide specific antibodies for the virus, to establish methods for isolating and collecting virus particles, to establish methods for treating the virus particles to attenuate their biological activity while maintaining their immunological activity, and to develop methods for assaying genes, antibodies, and antigens, and methods for producing neutralizing antibody-derived vaccines, which utilize the aforementioned biological materials derived from the virus to be obtained.